Abstract
This study describes the synthesis, theoretical investigations, and photocatalytic degradational properties of a new (pyrazine)(meso-tetrakis(4-tert-methoxyphenyl)-porphyrinato)-cadmium (II) ([Cd(TMPP)-Pyz]) complex (1). The new penta-coordinated Cd-II porphyrin complex (1) was characterized by various spectroscopic techniques, including FT-IR, NMR, UV-visible absorption, fluorescence emission, and singlet oxygen, while its molecular structure was studied using single crystal X-ray diffraction. The UV-Vis spectroscopic study highlighted the redshift of the absorption bands after the insertion of the Cd(II) metal ion into the TMPP ring. The co-coordination of the pyrazine axial ligand enhanced this effect. A fluorescence emission spectroscopic study showed a significant blueshift in the Q bands, accompanied by a decrease in the fluorescence emission intensity and quantum yields of phi(f) = 0.084, phi(f) = 0.06 and phi(f) = 0.03 for H-2-TMPP free-base porphyrin, [Cd(TMPP)] and [Cd(TMPP)(Pyz)] (1) respectively. Singlet oxygen revealed that the H-2-TMPP porphyrin produced the most efficient singlet oxygen quantum yield of (phi(Delta) = 0.73) compared to [CdTMPP] (phi(Delta) = 0.57) and [Cd(TMPP)(Pyz)] (1) (phi(Delta) = 0.13). In the crystal lattice, the [Cd(TMPP)Pyz] was stabilized through non-covalent intermolecular interactions (NCI), such as the hydrogen bonds C-H center dot center dot center dot N and C-H center dot center dot center dot Cg. Additionally, crystal explorer software was then utilized to measure the quantitative analysis of the intermolecular interactions in the unit cell of the crystal structure and established that the C-H center dot center dot center dot pi interaction dominated. The Natural bond orbital (NBO) analysis revealed that each molecule is stabilized by hyperconjugation and charge delocalization. As a photocatalyst, the coordination complex 1 showed excellent photocatalytic activity toward the degradation of Levafix Blue CA reactive dye (i.e., dye photo-degradation of 80%).